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Micron M500DC 800 GB SSD Review: Cloud And Web 2.0 Storage
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1. Bridging The Gap Between Consumer And Enterprise Storage

With the release of its M500DC, Micron continues a trend we've seen a lot of lately: dividing the SSD space into smaller pieces serviced by more purpose-built products. The relevant players take different approaches to this. For example, Intel cost-reduces its high-end enterprise drives, while Samsung adds enterprise-oriented features to its consumer architecture. Micron's M500DC takes the latter approach, incorporating higher-end functionality on a more desktop-class drive, rather than building a P400m (Micron P400m SSD Review: High Endurance MLC Is Here To Stay) with less expensive NAND. 

The M500 and its nearly-identical, Crucial-branded cousin offered good performance, large capacities, and reasonable pricing. In fact, you'll still find M500s in Best SSDs For The Money. And while Crucial went after cost-conscious consumers, Micron pushed its M500 at entry-level, read-focused enterprise customers. The M500DC fills a gap for the company between its M500 and P400m. Micron achieves this in much the same way as SanDisk (formerly SMART), taking 20 nm MLC NAND and applying a healthy dose of semiconductor and firmware know-how to stretch the attributes that matter for more demanding enterprise-focused customers.

Although Micron calls the segment it's targeting "Cloud/Web 2.0 Storage", a more general description would be a mixed-workload environment. The M500DC's endurance rating places it in front of read-focused SSDs with origins in the consumer space, while still clearly behind eMLC- and SLC-based drives. Not many SSDs fit that exact description, so comparisons are difficult. And this takes us back to advice we give over and over: know your workload. The more granular you get in predicting what your application does with storage, the better you can optimize total cost of ownership.

Micron M500DC
User Capacity
120 GB
240 GB
480 GB
800 GB
Interface
6 Gb/s SATA
Form Factor
2.5" 7 mm / 1.8" 5 mm
Sequential Read
425 MB/s
Sequential Write
200 MB/s
330 MB/s
375 MB/s
4 KB Random Read
63,000 IOPS
65,000 IOPS
4 KB Random Write
23,000 IOPS
33,000 IOPS
35,000 IOPS
24,000 IOPS
Power Consumption(Active Max)4 W
5 W
6 W
6.2 W
Endurance (TBW)
0.5 PB
1.0 PB
1.9 PB
1.9PB

Looking over its specifications, you can see that the M500DC is more than just a read-focused enterprise SSD. Write endurance falls between one to two Drive Writes per Day (DWPD), which is four to seven times higher than what you get from repurposed desktop technology, but below the 10 DWPD you'd see from Intel's SSD DC S3700 or Micron's P400m. It comes close to SanDisk and its Optimus Eco family, which is rated at 3 DWPD.

Topping out at 35,000 random write IOPS, the M500DC is also aligned with high-end enterprise SSDs. Unfortunately, read performance is a little underwhelming at 65,000 IOPS and 425 MB/s. Those are respectable numbers, but they're nowhere near the Optimus Eco and its 95,000 IOPS and 500 MB/s performance. They're also lower than most entry-level enterprise-oriented SSDs. We're not overly concerned yet, though. If you have a true mixed workload, the added write performance more than makes up for any shortcoming in read speed.

So, from a high level, the M500DC is set up to be more capable than most entry-level enterprise SSDs, but not as much so as the drives built to tolerate write-intensive tasks. For many of Micron's customers, price is going to determine which way they go. Unfortunately, as we often see, the company holds that information back. At higher capacities, however, we're expecting somewhere in the neighborhood of $1.15/GB, putting Micron's latest on par with Intel's SSD DC S3500. But let's see if we can form an opinion about the M500DC without the luxury of knowing what it costs.

2. A Look Inside Micron's M500DC

Though the M500DC shares its architecture with the M500, opening up the new SSD's chassis shows that they're actually quite different. The first thing you'll notice is how empty the PCB appears. There's so much room, in fact, that Micron left what we assume are debug headers across one side of the board. 

Micron has so much available space because the M500DC employs high-density NAND. The 800 GB model has 1024 GB of 20 nm MLC flash spread across eight packages. It's not of the eMLC variety. But still, Micron bins it specifically for more enterprise-oriented products.

The M500DC and M500 have the same type of NAND in common. However, when you open up an M500, you'll see all eight packages on one side of the PCB. The M500DC sports four per side. Each package contains eight dies, totally 1 Tb (128 GB) of capacity. Freeing up extra room allows Micron to also ship the M500DC in a 1.8" form-factor, in addition to the 2.5" drive we're reviewing. We didn't have a chance to benchmark the 1.8" model, however, you can see how the components would fit in a 1.8" footprint.

If you looked closely at the specifications on the previous page, two data points probably jumped out at you. First, the 800 GB M500DC has identical write endurance and lower random write performance compared to the 480 GB model. How is that possible? The more NAND your drive includes, the more flash there is to spread write amplification across and the higher endurance should be. It's just that simple.

When we opened the 800 GB model, we encountered the expected 1024 GB of NAND. So, what's going on with the other capacities to explain the difference? It turns out the the smaller drives include nearly double the amount of over-provisioning compared to Micron's 800 GB version. The 480 GB M500DC comes equipped with six packages, for instance, instead of the four you'd expect, yielding a raw total of 768 GB. As we know, the more NAND the controller has to work with, the more efficiently it can apply its software algorithms. 

Micron uses the same venerable Marvell 9187 that appeared on its M500, and heat is removed from it through thermal pads attached to the chassis. Of course, Micron applies its suite of enterprise-oriented firmware features (XPERT), which takes NAND management to a level appropriate for that market. I discussed the features at length in Micron P400m SSD Review: High Endurance MLC Is Here To Stay, but here are the highlights:

  • Redundant array of independent NAND (RAIN): An architecture that essentially provides device-integrated algorithms that are RAID 5 across the flash channels.
  • Advanced Read Mangement/Optimized Read (ARM/OR): This feature uses DSP algorithms to optimize NAND read and write locations.
  • DataSAFE: A data path protection mechanism that ensures all information is transferred correctly through the SSD structures.
  • Physical Power-Loss Protection: This feature uses on-board capacitors to continually store power for emergency use.
  • Reduced Command Access Latency (ReCAL): Utilizes well-managed background operations for quicker response times.

Additionally, the M500DC sports two 512 MB DDR3 DRAM packages, one on each side, yielding a fairly standard 1 MB per gigabyte DRAM to NAND ratio.

Finally, the top of board is populated with 12 capacitors used for power-loss protection.

3. How We Test Micron's M500DC
Test Hardware
ProcessorIntel Core i7-3960X (Sandy Bridge-E), 32 nm, 3.3 GHz, LGA 2011, 15 MB Shared L3, Turbo Boost Enabled
Motherboard
Intel DX79SI, X79 Express
Memory
G.Skill Ripjaws Z-Series (4 x 4 GB) DDR3-1600 @ DDR3-1600, 1.5 V
System Drive
Intel SSD 320 160 GB SATA 3Gb/s
Host Bus Adapter
LSI SAS 9300-8e
Tested Drives
Micron M500DC 800 GB
Comparison Drives
Micron P400m 200 GB
Intel SSD DC S3500 480 GB
Intel SSD DC S3700 800 GB
SanDisk Optimus Eco 400 GB
Seagate 600 Pro 200 GB
Graphics
AMD FirePro V4800 1 GB
Power Supply
OCZ ModXStream Pro 700 W
System Software and Drivers
Operating SystemWindows 7 x64 Ultimate
DirectXDirectX 11
DriverGraphics: AMD 8.883
Benchmark Suite
Iometer v1.1.0
Four Workers, 4 KB Random: LBA=Full, Span Varying Queue Depths
ATTO
v2.4.7, 2 GB, QD=4
Custom
C++, 8 MB Sequential, QD=4
Enterprise Testing: Iometer Workloads
Read
Write
512 Bytes
1 KB
2 KB
4 KB
8 KB
16 KB
32 KB
64 KB
128 KB
512 KB
Database
67%
100%
n/a
n/a
n/a
n/a
100%
n/a
n/a
n/a
n/a
n/a
File Server
80%
100%
10%
5%
5%
60%
2%
4%
4%
10%
n/a
n/a
Web Server
100%
100%
22%
15%
8%
23%
15%
2%
6%
7%
1%
1%

The Storage Networking Industry Association (SNIA), a working group made up of SSD, flash, and controller vendors, has a testing procedure that attempts to control as many of the variables inherent to SSDs as possible. SNIA’s Solid State Storage Performance Test Specification (SSS PTS) is a great resource for enterprise SSD testing. The procedure does not define what tests should be run, but rather the way in which they are run. This workflow is broken down into four parts:

  1. Purge: Purging puts the drive at a known starting point. For SSDs, this normally means Secure Erase.
  2. Workload-Independent Preconditioning: A prescribed workload that is unrelated to the test workload.
  3. Workload-Based Preconditioning: The actual test workload (4 KB random, 128 KB sequential, and so on), which pushes the drive towards a steady state.
  4. Steady State: The point at which the drive’s performance is no longer changing for the variable being tracked.

These steps are critical when testing SSDs. It’s incredibly easy to not fully condition the drive and still observe out-of-box behavior, which may lead one to think that it’s steady-state. These steps are also important when going between random and sequential writes.

For all performance tests in this review, the SSS PTS was followed to ensure accurate and repeatable results.

All tests employ random data, when available. Micron's M500DC does not perform any data compression prior to writing, so there is no difference in performance-based data patterns.

For comparison purposes, we evaluated the M500DC against similar products from Micron, Intel, SanDisk, and Seagate.

4. Results: 4 KB Random Performance And Latency

We knew going into our testing that the M500DC's random read performance wouldn't match most of our comparison drives. Iometer demonstrates exactly that, too. In fact, the only drive Micron beats at high queue depths is the company's P400m, its other enterprise-oriented SATA-attached SSD. The M500DC isn't positioned as a read-focused product though, so this result comes as no surprise.

The M500DC shines more brightly in random write performance. Its 800 GB model consistently exceeds the 24,000 IOPS claimed in Micron's datasheet. Compared to more read-oriented SSDs that hover in the 10,000 IOPS range, the M500DC delivers excellent performance.

We would have liked to test the 480 GB model as well. Micron says it should do 35,000 IOPS, and dropping that on the competition would have put it on equal footing as SanDisk's first-place Optimus Eco at 400 GB.

Average response time measurements put Micron's M500DC in the middle of the pack, which corroborates our IOPS testing.

Maximum response time lands slightly higher than the best enterprise-focused SSDs, though 26.54 ms is still a great result.

5. Results: Performance Consistency

Increasingly, we pay close attention to the performance consistency of enterprise-class SSDs. This is what separates a good drive from a great one when all of the corner case testing appears equal. Viewing the data with more granularity gives us insight on particular drive behaviors.

For the following tests, we subject Micron's M500DC and three comparison SSDs to 25 hours of continuous random 4 KB writes. We record IOPS every second, giving us 90,000 data points. We then zoom in to the last 60 minutes to more coherently visualize the results.

Overall, the M500DC performs well, even against more expensive drives. In fact, the M500DC substantially reduces the halo that we observed on Micron's P400m, though it can't quite match the tighter grouping delivered by SanDisk and Intel.

Looking at the distribution of data points reveals another interesting behavior.

Almost 96% of all data points are within 0.06 ms of each other, which is astounding. In comparison, SanDisk's Optimus Eco did not have any 0.06 ms-band that contained more than 58% of its data points. Really, our only complaint is the outliers around the 1.7 ms mark. Still though Micron's M500DC maintains its rated specification on nearly 98% of our measured data points. Even the outliers are at a respectable 18,000 IOPS.

Normally, we only post consistency data on a drive once it reaches steady-state. With the M500DC, getting to this point was more difficult than usual. The chart below shows a fresh M500DC with our random write workload applied.

It took nearly nine hours before the drive finally hit steady-state. We also found that if you aren't careful, the drive will trigger the TRIM command, and you get back to fresh out-of-box performance in a hurry. For what it's worth, only enterprise SSD reviewers get upset when a drive recovers its speed like this. And in case you're wondering, that stretch of data at the beginning lasts for almost an hour, with IOPS ranging from 66,000 to 78,000!

6. Results: Enterprise Workload Performance

Our next set of tests simulates different enterprise-oriented workloads, including database, file server, Web server, and workstation configurations.

The database workload (also categorized as transaction processing) involves purely random I/O. Its profile consists of 67% reads and 33% writes using 8 KB transfers.

I have to say I was a little surprised at the outcome of this test. Not only does Micron's M500DC blow by the entry-level offerings, but it also maintains a clear advantage over the rest of the field, too. The drive's excellent write performance is enough to make for its lower read rate.

In the file server workload, which consists of 80% random reads of varying transfer sizes, the M500DC gives us another strong showing, only trailing SanDisk's Optimus Eco at high and low queue depths. In the sweet spot (a queue depth between eight and 32), the M500DC is a clear winner.

The Web server workload (100% reads of varying transfer sizes) exposes one of the M500DC's weaknesses: pure read-based transactions. At higher queue depths, it's only able to match the P400m, while trailing the other contenders by a wide margin.

Finally, the workstation benchmark (80% reads, 80% random) puts Micron's M500DC back near the top. While it consistently trails Intel's SSD DC S3700 and SanDisk's Optimus Eco, it clearly beats the rest of the field.

Overall, the M500DC performs well in our mixed workload tests, only falling behind on the read-only metrics. These results should be even higher if we retest using Micron's 240 and 480 GB models. I'd say this is a considerable accomplishment for a drive that owes a lot of its design to a cost-optimized consumer SSD.

7. Results: Sequential Performance

Once again, the M500DC posts modest, but not great read performance. At 450 MB/s, it trails SanDisk's Optimus Eco and Seagate's 600 Pro by nearly 100 MB/s.

Sequential write performance is a bit worse. At 405 MB/s, the M500DC consistently beats its specification. But that still puts it near the bottom of the field. It's also nowhere near the Eco's crazy 560 MB/s.

Clearly, sequential performance is not one of the M500DC's strong suits. Fine-tuning SSD firmware is a series of give and takes. Bolstering throughput in one measurement often decreases it in another one. Fortunately, Micron is clear about the workloads this new drive is intended to address. While it excels in a number of enterprise-oriented tasks, the best we can say about the M500DC in sequential transfers is that it's adequate.

8. Results: Enterprise Video Streaming Performance

Video streaming is a demanding workload within the enterprise space. Companies want more HD streams with higher bit-rates and no stuttering. A storage solution well-suited for enterprise-class video delivery has completely different capabilities than something designed for databases. At the end of the day, you're basically looking for exceptional large-block sequential write performance. You also need a high level of consistency that traditionally isn't seen from consumer SSDs. For a more in-depth analysis, take a look at page 10 of Intel SSD 910 Review: PCI Express-Based Enterprise Storage.

As we saw in our sequential testing, the M500DC does not post a very high sequential write rate. But what it lacks in throughput is more than made up for by consistency.

The graph above is highly averaged, with each point representing 800 MB, but the consistency is still evident. In fact, the range from peak to trough is roughly +/- 1% of the average. We run this test 100 times on each drive, and every cycle looks exactly like the chart we're showing you.

Due to limits of Excel, I can't chart out the individual 8 MB writes, but I assure you that they're incredibly consistent. In fact, in order to maintain 400 MB/s (which is 25 MB/s higher than Micron's spec), we only need a 32 MB buffer. That is outstanding. 

9. New: Power Consumption, Detailed

Power consumption, with regard to solid-state storage, is an interesting topic. In most reviews, you typically see power averaged for idle, in a sleep state, and under load. Although that's useful, those numbers don't give you the entire story of how SSDs use power. In order to fully understand draw, we need instrumentation to accurately measure voltage and current. In our testing, we use a high-precision DC source that is capable of sourcing 30 W at 5 V. It is also able to, with a high level of accuracy, measure the output voltage and current draw at 5000 samples per second. The source is then spliced into a SATA power cable, allowing us to calculate consumption.

Now that we can measure the exact power draw of any SATA-attached SSD, interesting trends start showing up. Every attribute, from power-up, to sequential and random workloads, and even the TRIM command shows up as a distinct power level unique to each drive. Power consumption is also intrinsically linked to performance. Of course, this shouldn't be news to anyone familiar with the way electronic components work. Generally, the harder you push a piece of hardware, the more power it draws. What is news, at least to us, is that performance variations happening at the sub-millisecond level are observable in a drive's power draw.

This first chart illustrates a full battery of benchmarks on Micron's M500DC. At the start, you can see power-on levels, including in-rush. Once the device is recognized by the system, it enters an active idle state. Next, we run our different workloads, including 4 KB random reads and writes, sequential reads and writes, and finally our server workloads. As you can see, each metric exhibits its own distinct power level. In general, sequential writes draw the most power, while reads draw the least.

In mixed workloads, you can visualize the read/write balance. For example, the database profile has the highest power consumption because it biases most heavily to writes, while the Web server test sit at the opposite end of the spectrum.

In this particular case, I only ran each test for 10 seconds to illustrate my point. On the next page, however, I'll get into the official results based on much longer durations.

Next, I investigated use of the TRIM command by first writing a 100 GB sequential file to the drive. You see the final few seconds of that at the start of my line graph. Once the write completes, I open up the Recycle Bin and delete the file, which causes a short impulse near the center of the chart. Finally, the TRIM command is seen actually executing.

The graph looks really simple, but there are quite a few observations we can make. As soon as the sequential write completes, the M500DC transitions back to active idle almost immediately. This shows that the SSD not only wrote the data as soon as it was received, but also kept up with its internal tasks (like wear leveling and garbage collection). On lower-performance SSDs, I've seen continued high power draw for as long as 10 seconds after the write supposedly finished. Also interesting, once the Recycle Bin is emptied, an additional 11 seconds pass before Micron's drive actually triggers the TRIM command. At that point, the M500DC only needs 2.3 seconds to execute it. On some drives, this can take 10 to 20 seconds to finish, making Micron's offering one of the quickest I've ever seen.

If you've read my previous enterprise-oriented drive reviews, you're already familiar with my Enterprise Video testing, where I look at large block sequential writes across each SSD's entire span. I then evaluate the drive based on the frequency and severity of its performance dips. Almost every SSD demonstrates some sort of unique, periodic pattern normally attributed to its background tasks.

When I started running our power testing, I noticed the same patterns. The graph above shows our typical Enterprise Video test, but instead of just recording timestamps after each block was written, I also measured power. And every single dip in performance matches up with dips in power use. More interesting, both dips (performance and power) are of the same general magnitude. In this case, the background tasks causing the dips stress the drive less than the actual workload being applied.

Finally, when it comes to talking about mobile-oriented SSDs, power consumption is almost always related to a drive's ability to enter idle and sleep states. This is due to the fact that utilization of consumer drives is typically low, and sleep states can add precious minutes to battery life. Enterprise customers have a completely different set of requirements and expectations. Their applications typically have a very high duty cycle, and therefore do not spend much of their lives sleeping. In many cases, low-power states can even be detrimental to enterprise applications, since going in and out of them takes time, and small delays are potentially costly. 

In our testing, when we talk about idle power, we are referring to Active Idle. SSDs enter idle and sleep states either through Host-Initiated Power Management (HIPM) or Device-Initiated Power Management (DIPM). Measuring DIPM-enabled SSDs, it can be difficult (going only on power consumption) to determine the state a drive is in. This is especially true for Partial Idle, because time-to-active is less than 10 microseconds.

10. Results: Power Consumption

With a firm understanding of how our power testing works, let's check out the results. First up is Active Idle. 

We're adding Samsung's 843 to the chart, since it's based on the notoriously frugal 840 Pro. Micron's M500DC hovers around 1 W through most of our measurement. That's roughly 50% higher than the two Intel drives and almost three times higher than the 843. There are IT professionals out there who like using enterprise storage in laptops and portable workstations. Due to its lack of DIPM and relatively high idle power, the M500DC would not be an ideal SSD for those on battery power, though.

A look at the power consumption from our sequential and random workloads shows the M500DC in the middle to high-end of the field. Unfortunately, the discipline where the M500DC excels, random write performance, is also where it draws a lot of power. Excluding the P400m, Micron's M500DC is over 1 W higher than the other SSDs in that test. 

Once again, the M500DC is in the middle of the field. Granted, the SSDs we're testing include several different capacities, and fewer components in a drive mean less power consumption. So, it'd make sense that the M500DC and SSD DC S3700 are near the bottom. In an ideal world, all SSDs would be sampled in identical capacities to make comparisons easier. But that's just not the case.

Don't overlook the fact that Micron rates its M500DC at 6.2 W, and we were unable to push it past 5 W in any of our tests.

11. Creating A New Mid-Range Enterprise Market

Over the last year, the enterprise-oriented offerings from Micron have been a mixed bag. While we really liked its PCIe-based accelerators, the P400m couldn't quite stand up to its competition. That was especially disappointing considering the company's expansive NAND portfolio and firmware expertise. Christopher and I have always said that SSD vendors with NAND production capabilities should always come out on top. With the M500DC, Micron lives up to that expectation with a product that offers good performance at what we expect will be attractive pricing.

When it comes to comparing SSDs, you already know that there are many variables to consider: price, performance, endurance, value-adds, and more. Micron's M500DC should make you think a little harder about each if you're in the position to outfit a big organization with solid-state storage. It doesn't fit into some of the more traditional markets carved out in recent months. Outside of SanDisk's Optimus line, there simply aren't many drives that match its specs. And the M500DC doesn't lead in many categories, either. But where it does shine, it bests an impressive list of relatively comparable products.

Let's start with the bad. In straight read performance, Micron trails the pack. Demonstrating lower sequential and random read throughput, the M500DC is not suited for read-heavy applications. Instead, you'd be better off tapping Micron's M500 or Intel's SSD DC S3500.

Write performance favors the M500DC more, and it gives pricier SSDs a run for their money. Even though the 800 GB model's specs trail the 480 and 240 GB versions, the drive we're reviewing still outclasses most entry-level enterprise-oriented SSDs.

Enterprise workloads, so long as they involve writes, show Micron's latest excelling. The M500DC posts incredibly high numbers, particularly in our test designed to replicate the behavior of a database. 

Write endurance has the M500DC in the middle of a distinguished pack. It's much better than the read-focused entry-level drives, but naturally trails the eMLC- and SLC-based offerings. Further, endurance is a tricky spec to evaluate. It used to be that endurance was closely related to the type of NAND used. But Micron (and SanDisk) extends the life of its flash well beyond the stuff most consumers encounter. They're consequently able to offer better $/TBW, which is what consumers are, presumably, asking for. 

So, it all comes back to what enterprise customers want in an SSD. Micron believes it knows, and it tailors the M500DC's performance to match. For mixed-workload environments, the product of those efforts performs as well as anything on the market. And for where we expect its price to land, the M500DC should end up in a class by itself.